World record-holder Arlen was last week earmarked by Great Britain's Ellie Simmonds as someone who would pose her a major threat, given the American had taken Simmonds' world records in the S6 100 metres and 400m freestyle – the two events in which Simmonds won gold at the Beijing Games.

The IPC received evidence compelling them on Tuesday to assess Arlen and found she was ineligible for competition.

The United States appealed and the 17-year-old is now set to be reclassified on tomorrow's opening day of the swimming programme.

An IPC spokesperson said: "She was reclassified on Monday and found non-eligible; she did not meet the eligibility criteria for her chosen sport. She must be reclassified tomorrow morning."

Arlen, a former junior state champion, returned to swimming last year after a neurological virus called transverse myelitis affected her spinal cord in 2006 and left her in a vegetative state for two years, and set the world records at the US trials in June.